YELLOWSTONE NATIONAL PARK, Wyo. – Warmer temperatures, longer and more volatile fire seasons, shorter winters, less snowfall and significant changes in the dominant species of plants: The iconic park you see here today will be fundamentally altered by global warming in the coming decades.
“That conclusion is pretty much inescapable,” said John Gross, an ecologist with the National Park Service's Climate Change response program. “It's really more a question of the when and how it occurs than if.”
Scientists have already documented dozens of changes in the park in the past 50 years, including 30 fewer days with snow on the ground per year, 80 more days above freezing per year at the northeast entrance and higher average temperatures overall, especially during the nighttime. The ramifications are huge, but exactly what that means for the park in the future is hard to pinpoint.
“We’re kind of in the middle of it, and we’re now thinking of those historic trends as more of an indicator for us about where we’re going into the future,” said Ann Rodman, director of geographic information system operations for the park.
The heat is on: Extreme temperatures expected through 2022
Weather, fire extremes could become more common
A hotter, drier climate in Yellowstone means extreme weather events, and the frequency and severity of fires could become more common, Rodman said. Snow melting faster in the spring increases the potential for flooding. A lower snowpack means less water to last through the summer, causing plants to potentially die out sooner and reducing the vegetation animals feed on. A longer growing season, where winter starts later and ends earlier, makes drought more likely in the middle of the summer.
“Things are becoming a problem now that weren’t a problem in the past,” Gross said.
Those events are difficult to predict because of all the variables that must come into play each year and each season.
“You have to have all the right things come together. The potential for those things are going to increase in the future,” Rodman said. “When we start getting those more common unusual events we aren’t set up for – those are the kinds of things we’re starting to pay attention to.”
Yellowstone and other ecosystems have undergone immense change due to natural climate cycles in the past. What makes it so different today is the timescale on which these changes are happening. Big temperature shifts used to take 5,000 to 10,000 years. Now, they're happening in decades, Rodman said.
"One of the things about climate change that I'm beginning to appreciate is the rate and speed at which this is happening, which is kind of the unprecedented part in all of this," she said.
The implications on the park’s animals and plants are immense but because the changes are occurring far more rapidly than in the past, scientists don’t have a model to predict what Yellowstone will look like 50 or 100 years from now.
“We don’t have a past we can look back on and say if something happens this fast, this is how things are going to react,” she said. “You really don’t know, if the vegetation changes, how the animals are going to react to it, but they certainly will."
Alpine meadows at risk
The park is already changing due to warmer temperatures. Parts of the park have been invaded by plants that take advantage of the newer climate conditions and can out-compete the native vegetation for moisture. “At the lowest elevations of the park, we’ve seen a huge change in vegetation in the last 10 years,” Rodman said.
It’s not unnatural for the dominant forest type in any particular area to change overtime. But the timescale that happens on is usually much longer, Gross said.
“The big deal with climate change is all this is happening really really fast," he said. "A transition that might have previously occurred over several hundred years that’s going to occur now over a really short period, maybe 50 years or 100 years.”
Add in the fire threat, and you’ll see the problem: What happens when plant species that have survived in an area for thousands of years can’t come back after a large chunk of land is burned? Plants that didn’t previously grow in that area may spring up because they can survive the hotter, drier climate now in place.
“With climate change, it's going to be really difficult to figure out in some cases what an invasive species is,” Gross said. “The park will be really changed.”
The highest elevations in Yellowstone, where trees give way to alpine meadows, could be some of the most affected by climate change, said Tom Olliff, head of landscape conservation and climate change for the National Park Service's Intermountain Region, which covers more than 80 different parks, including Yellowstone, where he's worked for more than 30 years.
"In some scenarios, we’ve projected that those would disappear and you’d have all forests, and clearly that’s going to hurt things," including animal species such as the American pipit, marmot and pika, Olliff said.
With a large uptick in fire frequency and severity, Yellowstone will look much different. In 50 years, the omnipresent lodgepole pine may no longer dominate, for instance. "It would be a whole different Yellowstone," he said.
Invasive plants could be OK
Yellowstone and other ecosystems around the U.S. and the world have evolved to handle wildfires and natural changes that occur slowly over time. But with climate change, the old vegetation might not grow back after a fire and instead a different species, one more tolerant to warmer and drier conditions, might take its place – and that's new.
“There’s going to be plants that are more conducive to growing in hotter, drier climates either from lower elevation moving up or from outside the park coming in,” Rodman said. “Our whole way of dealing with that in the past has been keeping the things that have always been here here and keeping out things that are moving in. We’re going to have to rethink all of that.”
That could mean letting plants move into the park even though they are technically invasive but are native to areas outside its borders. Rodman’s fear is we won’t make that change in mindset quick enough.
“National parks have been all about preservation and really managing things with a look to the past. And we have to switch over and be more forward looking and managing for change as opposed to preservation,” she said. “I worry about our ability to make that switch in time to be effective.”